Various transition metal complexes have hitherto been employed as catalysts for organic syntheses, and intensive studies have been conducted on syntheses using noble metal complexes as catalysts taking advantages of their stability and easiness in handling though they are expensive. In particular, studies have been directed to asymmetric catalysts to be used in asymmetric syntheses, such as asymmetric isomerization, asymmetric hydrogenation, and the like. Of the reported asymmetric catalysts, metal complexes formed between an olefinic rhodium complex and an optionally active tertiary phosphine are especially well known. Such complexes typically include a rhodium-phosphine complex using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as BINAP) as a ligand as disclosed in Japanese Patent Application (OPI) No. 61937/80 (the term "OPI" as used herein means "unexamined published application"). One example of application is described in Inoue et al., Chemistry Letters, pp. 1007-1008 (1985), in which they obtained citronellol by asymmetric hydrogenation of geraniol or nerol using various rhodium-phosphine catalysts in an optical yield of 66%.
On the other hand, known ruthenium complexes, though there are not so many reports as compared with rhodium complexes, include those having BINAP or 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as T-BINAP) as a ligand, i.e., Ru.sub.2 Cl.sub.4 (BINAP).sub.2 (NEt.sub.3) (wherein Et represents an ethyl group, hereinafter the same) and Ru.sub.2 Cl.sub.4 (T-BINAP).sub.2 (NEt.sub.3), as reported in Ikariya et al, J. Chem. Soc., Chem. Commun., pp. 922 (1985). However, the state-of-the-art ruthenium complexes are not satisfactory in stability as well as asymmetric yield.
Although metallic rhodium provides excellent complex catalysts, it is expensive due to limitations in place and quantity of production. When used as a catalyst component, it forms a large proportion in cost of the catalyst, ultimately resulting in increase in cost of the final commercial products. While metallic ruthenium is cheaper than rhodium and appears promising as a catalyst component for industrial application, it still has problems in its activity to cope with precision reactions and its range of application.
Therefore, it has been keenly demanded to develop a catalyst which is inexpensive, has high activity and durability, and catalyzes asymmetric reactions to attain high optical yields, i.e., to produce reaction products having high optical purity.